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The Harris No. 1 Mine in Boone County, WV, has been longwalling the Eagle Coalbed for over 30 years. Harris has experienced numerous interactions associated with the extensive room-and-pillar and longwall mining operations that have been conducted in the overlying No. 2 Gas Coalbed. The problems have included roof falls, excessive rib sloughage, and gate road and bleeder entry closure. A detailed evaluation of the multiple-seam experiences at Harris No. 1 Mine was done as part of NIOSH's nationwide multiple-seam mining case history database. One observation was that smaller, critically loaded, upper-seam pillars seemed to cause more severe ground conditions than wider pillars. The LaMODEL program was used to investigate this. Results confirmed that critical-sized pillars transmit the highest amounts of stress to adjacent seams. In addition, the data suggest that the probability of a major multiple-seam mining interaction increases when the depth of cover is 1,000 ft or greater and when the Eagle Seam pillars have an ALPS stability factor of less than 1.50.